Method for electroplating a plastic substrate

ABSTRACT

A method for electroplating a plastic substrate includes the following steps, a plastic substrate is firstly provided. The plastic substrate is then pretreated to form a noble metal coating. The noble metal coating is coated with a copper coating. A first chrome coating is electroplated onto the copper coating using a first electrolyte including a chromic component. A second chrome coating is electroplated onto the first chrome coating using a second electrolyte including a chromyl component.

BACKGROUND

1. Field of the Invention

The present invention relates to a method for electroplating a plastic substrate.

2. Discussion of the Related Art

Electroplating is an attractive and effective process for improving corrosion resistance and metallic appearance of covers for mobile devices. Many covers molded from plastic are processed to form plated metal coatings on surfaces thereof using electronic plating.

A typical electroplating process forms a nickel coating on the covers. However, the nickel coating is an irritant to the skin, which may cause irritation to the skin.

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWING

Many aspects of the method for electroplating a plastic substrate can be better understood with reference to the following drawing. The components in the drawing are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the method for electroplating a plastic substrate.

The drawing is a flow chart of an exemplary embodiment of a method for electroplating a plastic substrate.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring to the drawing, a method of an exemplary embodiment for electroplating a plastic substrate may includes steps 100 to 500.

In step 100, a plastic substrate made from one of acrylonitrile butadiene styrene (ABS), poly methyl methacrylate (PMMA), and polycarbonate (PC) is provided.

In step 200, a surface of the plastic substrate is metalized to form a noble metal coating. During the pretreatment, the surface of the plastic substrate is first roughened by etching. The etching of the plastic substrate allows the noble metal coating to be attached onto the roughened plastic surface in a subsequent process. The etching process may be carried out, for example, using chromic acid, chromosulfuric acid, or potassium permanganate etching solution. It is to be understood that the etching process also can be carried out in a plasma chamber. An associated cleaning step cleans the plastic substrate. Subsequently, the surface of the plastic substrate is activated by immersion into an activating solution containing a hydrochloric acid, a polyamide acid, and a noble metal salt. During activation, a noble metal is separated from the activating solution and deposited on the surface of the plastic substrate to form the noble metal coating on to the roughened surface of the plastic substrate. The noble metal coating may include palladium.

In step 300, a copper coating is electroplated onto the pretreated surface of the plastic substrate. The electroplating forming the copper coating is carried out by immersing the plastic substrate into an electrolyte including at least one of copper sulfate and copper pyrophosphate, with the pretreated surface of the plastic substrate being electronically connected to a cathode of an electrical source, and the electrolyte being electronically connected to an anode of the electrical source. It is to be understood that the copper coating also can be formed by physical vapor deposition.

In step 400, a first chrome coating is electroplated onto the copper coating. The electroplating for forming the first chrome coating is carried out by using a chromic electrolyte including a chromic salt and a buffer agent, at a temperature from about 28° C. to about 52° C. and a current density from about 3 to about 20 ampere per square decimeter. The chromic salt may be one of chrome sulfate and chrome chloride. The buffer agent may be boric acid.

In step 500, a second chrome coating is electroplated onto the first chrome coating using a chromyl electrolyte including a chromyl component and sulfate acid, at a temperature from about 30° C. to about 60° C. and a current density from about 5 to about 40 ampere per square decimeter.

As such, the plastic substrate may be coated with a copper layer and two chrome coatings, which improves the anti-corrosion and anti-abrasion of the plastic substrate.

It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention. 

1. A method for electroplating a plastic substrate, comprising the steps of: providing a plastic substrate; metalizing the plastic substrate; forming a copper coating onto the noble metal coating; electroplating a first chrome coating onto the copper coating using a first electrolyte including a chromic component; and electroplating a second chrome coating onto the first chrome coating using a second electrolyte including a chromyl component.
 2. The method as claimed in claim 1, wherein the plastic substrate is made from one of acrylonitrile butadiene styrene, poly methyl methacrylate, and polycarbonate.
 3. The method as claimed in claim 1, wherein the noble metal coating is made of palladium.
 4. The method as claimed in claim 1, wherein the copper coating is formed by electroplating.
 5. The method as claimed in claim 1, wherein the copper coating is formed by physical vapor deposition.
 6. The method as claimed in claim 1, wherein the first electrolyte includes boric acid.
 7. The method as claimed in claim 1, wherein the chromic component is one of chrome sulfate and chrome chloride.
 8. The method as claimed in claim 1, wherein the electroplating for forming the first chrome coating is carried out in the first electrolyte at a temperature from about 28° C. to about 52° C. and a current density from about 3 to about 20 ampere per square decimeter.
 9. The method as claimed in claim 1, wherein the second electrolyte includes sulfate acid, the electroplating for forming the first chrome coating being curried out in the second electrolyte at a temperature from about 30° C. to about 60° C. and a current density from about 5 to about 40 ampere per square decimeter.
 10. A method for electroplating a plastic substrate, comprising the steps of: providing a plastic substrate; forming a noble metal coating on the plastic substrate; forming a copper coating onto the noble metal coating; electroplating a first chrome coating onto the copper coating using a chromic electrolyte; and electroplating a second chrome coating onto the first chrome coating using a chromyl electrolyte including a chromyl component.
 11. The method as claimed in claim 10, wherein the plastic substrate is made from one of acrylonitrile butadiene styrene, poly methyl methacrylate, and polycarbonate.
 12. The method as claimed in claim 10, wherein the noble metal coating is made of palladium.
 13. The method as claimed in claim 10, wherein the copper coating is formed by electroplating.
 14. The method as claimed in claim 10, wherein the copper coating is formed by physical vapor deposition.
 15. The method as claimed in claim 10, wherein the chromic electrolyte includes boric acid and a chromic salt.
 16. The method as claimed in claim 15, wherein the chromic salt is one of chrome sulfate and chrome chloride.
 17. The method as claimed in claim 10, wherein the electroplating for forming the first chrome coating is curried out in the chromic electrolyte at a temperature from about 28° C. to about 52° C. and a current density from about 3 to about 20 ampere per square decimeter.
 18. The method as claimed in claim 10, wherein the chromyl electrolyte includes a chromyl component and sulfate acid, the electroplating for forming the first chrome coating being curried out in the chromyl electrolyte at a temperature from about 30° C. to about 60° C. and a current density from about 5 to about 40 ampere per square decimeter. 